A-162 Prevalence of EDTA-Dependent Pseudothrombocytopenia: A 10-Year Analysis

Abstract Background Pseudothrombocytopenia is an alteration in platelet count caused by the formation of microaggregates induced by the anticoagulant EDTA in collection tubes. It is a rare condition with a prevalence of 0.01% to 2%, but it is clinically and laboratorially significant as it can lead to misdiagnosis and hinder accurate interpretation of hematological elements. Therefore, it is essential to apply the appropriate approach when handling cases of pseudothrombocytopenia. This can include manual platelet counting using the Fonio method, reanalysis using sodium citrate tubes, manual vortex mixing, or reprocessing after incubation at 37°C in a water bath. Analyzing pseudothrombocytopenia cases using big data is crucial to raising awareness of this finding, thereby preventing diagnostic errors and avoiding unnecessary patient concerns. Methods A total of 2,025,185 CBC measurements from a Brazilian outpatient population (2015–2025) were analyzed to identify cases of EDTA-dependent pseudothrombocytopenia using DataR. The study population was also assessed based on sex, age, and other CBC parameters. Samples were analyzed using the ADVIA 2120 Hematology System™, which distinguishes platelets using two-angle laser light scattering flow cytometry. In our practice, we visually evaluate blood smears for all thrombocytopenia cases (platelet count <150,000/mm³) and according to characteristic histogram patterns. In cases of platelet aggregation, vortex mixing was applied, and platelet counts were manually assessed under a microscope using the Fonio method. Results Between 2015 and 2025 we analyzed 2,025,185 CBC results, 64% (1,292,738) were from female patients, with a mean age of 54 ± 23 years. The following mean CBC values were observed: RBC: 4.59 ± 0.54 × 106/mm³, HGB: 13.44 ± 1.56 g/dL, WBC: 7,005 ± 3,528/mm³, and PLT: 350 ± 876/mm³. Thrombocytopenia was found in 3.25% (N=66,017) of cases, more common in male patients (56%; 36,819), with a mean age of 66 ± 22 years. EDTA-dependent pseudothrombocytopenia occurred in 0.035% (N=709) of the population. It was more frequent in female patients (70%; p<0.01), while the mean age (64 ± 23 years; p=0.191) was similar to that of thrombocytopenia cases. This suggests a higher prevalence of EDTA-dependent pseudothrombocytopenia in females but no significant correlation with patient age. Conclusion EDTA-dependent pseudothrombocytopenia affected 0.035% of our population, consistent with the prevalence in the literature, primarily affecting older individuals. It was more frequent in females compared to true thrombocytopenia. In this context, it is essential to evaluate blood smears in patients with low platelet counts, considering the histograms and flags of hematology analyzers, as well as to follow protocols that allow for an accurate platelet count in these cases, preventing diagnostic errors.